For a 75. Read some old threads on ammeter and a few had problems with frying wires and threats of fire from ammeter.

Should I switch to a voltmeter for 75 or work with ammeter. For a nice driver not a resto. Id like to keep ammeter if I can ensure preventing the fried wire risk.

Any advice appreciated.

Also Ammeter is correct for the 75 but I'm having trouble locating an aftermarket replacement. They go to 74 and continue at 77 but 75 and 76 are hard to find. Anyone know reason?

 

I am assuming there is a face diff since I am sure the meter itself is the same, if your face is good you could swap out the meter with an earlier year, I did that with the temp gauge in my 73, using an after market gauge with the orig face.

 

Check the Mad Electrical site. I believe it states that an ammeter should not be used with an alternater that is 100 amps or higher.
Later,
Sly

 

FWIW... An ammeter gives you no useful info on the state of the electrical system, it only tells you the current draw of the system and if you have a short or bad wires or something in the wiring this will give you the wrong impression if you dont know how to determine what the guage reading means. The volt meter actually tells you the state of charge in the system in a high or low fashion and any unusual draw on the syatem always brings the reading down so you know that somethings not right. It allows you to compare the charge voltage to the assumed battery static voltage (12.5v) and anything at or below this level is not charging (should be min 13.5v).

 

Great ideas Fevre. Thanks.

 

The Mad site had great info. Thanks for the lead!!! Mine currently has 63A but I wasa thinking of bumping it up. Timely info Sly. Thanks again!!

 

Looks like the voltmeter is the way to go for me as I am most interested in functionality of charging system. Thanks Vettevic!!

 

think of it like this an ammeter becomes a part of whatever circuit you tap into. so if you have a high amp circuit, you need to ensure you use lager guage wiring to keep things from buring up. when you dont, that what causes fires, no the ammeter itself. 20 guage or higher in this case.

a volt meter juts taps into the circuit and thus the need for a heavy gague wire is less. The stock guage in the older vettes is a volt meter, meaning it taps into the charging circuit. why you would need an ammeter unless running soem kind of computer controled system where it counts more is beyond me. but do what you like

 

Thanks sweethence!!. The ammeter is stock but you reinforced my switch to voltmeter.

Do I need to run the volt meter in series with the alternator hot wire or in parellel?

Or is there a better way (where to contact) to hook it up?

 

The volt meter is just a meter in a parallel circuit. It can be wired to any direct feed line from the alt or battery just make sure that the guage is not powered when the ignition is off cause it does have a slight draw.

 

When your battery is low the ammeter shows more + draw, as the battery gets closer to full charge it draws less current from the system and the meter reads closer to 0. With a voltmeter you cannot tell what level you battery is at when the car is running, if your alt is good the system will show full voltage but will show low voltage if the key is off.

I leff my key in the on position last night and ran the battery down, jumped it then drove around until the needle was almost back to zero on the ammeter so battery is pretty much charged back up again.

Not saying one is better or worse than the other but each does give info that can be usefull.

 

EXCEPT: I WILL say an ammeter IS better for the reasons you stated. You can have a dead battery and it will look fine with a voltmeter after you jumpstart the engine.

I'd bet the reason they went to voltmeters was that they are much less expensive to wire into the car relative to either a full current ammeter or paralell circuit ammeter. Also since the later ammeters were wired in paralell with a second current wire, a loss of that paralell wire can roast ammeter wiring or possibly the converse.....

 

Strong arguments both ways. If no threat of toasting wires with ammeter and I have power at gauge I might stay with stock. If not and I have to rewire, probably voltmeter.

Tough call. Thanks to all for the info. Allows me to make an informed decision.

 

If you're all about functionality, ditch the clock and run both.

trw

 

When I bought my 77, I was used to an ammeter & ready to change.
I called my CE (Customer Engineer, Main frame computers, one of the best in the world) to find out which was better.
The voltmeter.



http://forums.corvetteforum.com/show...ight=voltmeter

http://forums.corvetteforum.com/show...ight=voltmeter

PS The idea of running both is good for those who already have an ammeter.
I put an oil temp. in place of the clock.

 

Just wanted to run this one back to the top.


TTT

 

I agree that the ammeter is a better indicator of current drain amd battery health. Alternator output voltage can be check periodically. The reason ammeter connections are alleged to cause fires is that bubba replaces fusible links with normal wire and installs twice the alternator he needs and then overhets the circuit!

 

This is not true. The ammeter tells you the current draw of the ckt yes but has nothing to do with the condition of the battery. The reason I say this is because the battery and the alternator are not the only components in the complete circuit, therefore you are getting a reading of the entire circuit drain in amps. The ONLY way to correctly or accurately tell the charge current of a battery is to remove it from the circuit and charge it independantly of the cars electrical system and measure it that way, but this does not tell you if the battery is bad, only the charge current. A load test is the best way of checking a battery. You will NEVER read 0 (zero) on an accurate ammeter in a running vehicle because the ignition, charge exciter in the alternator, engine monitoring switches (ie: temp, oil) and inherent resistance in the connections of the grounds to the frame etc., all take current to operate and this is read by the ammeter. the purpose of the guage is to detect a problem while it happens so you can get off the road. An ammeter will still read a draw if the alternator is bad cause the battery is still supplying the current to the circuit, where a voltmeter will tell you the alt is not charging and the battery is getting weak. There is more to it than just this but usefulness to the layperson should be considered and a voltmeter is the best choice.

 

If you had a bad connection at the batt. the volt meter will show ok but there may be no current flow also I think a loose belt will be more evedent in the ammeter. I like the old ammeter.

 

Keep in mind that the way the ammeter is set up in the 'Vette, (by reading the potential difference between the battery supply voltage and the charging system voltage), if the meter shows a positive deflection the battery is beign charged. Pretty simple and reliable.